In certain large-scale printing systems, printheads are used to eject ink onto a substrate to create the desired image, for example, on substrates such as museum displays, billboards, sails, bus boards, and banners. In some of these printing systems, the printheads receive ink from an ink supply or reservoir and use a so-called “drop on demand” ink jet process. With this type of process, ink is ejected from one or more nozzles of the printheads only when a piezoelectric crystal in the printhead is actuated. In particular, the piezoelectric crystal creates a pulse in the ink so that the ink expels through the nozzle as a droplet. To create the image, a carriage which holds one or more printheads scans or traverses across the substrate while the printheads deposit ink as the substrate moves. In some other systems, the substrate moves underneath a stationary set of printheads as the printheads deposit ink.
Generally, the printheads are under the direction of a controller or CPU. Digital information related to the desired image is stored within the memory of the controller or CPU. A software application in the CPU instructs the printheads to deposit ink in a particular sequence based on the stored digital information to generate a predetermined image on the substrate. Some of these systems use different colored inks to create the desired images. For instance, black, yellow, cyan, and magenta colored inks are commonly employed alone or in combination to generate the image. Other systems use additional colored inks, such as light black, light yellow, light cyan, and light magenta to create images with higher resolution. In general, images created with a greater number of colored inks are typically of higher quality than those generated with fewer colored inks.
Regardless of the number of colored inks used to generate the images, each printhead receives ink of a particular color from a respective container or reservoir. Hence, the ink reservoir or container associated with each printhead must contain the colored ink identified with each printhead, otherwise the printhead will deposit the incorrect colored ink.
As ink in the various containers runs out, an operator has to replace the containers with a full supply of ink. This is done, for example, between printing operations. However, the operator may inadvertently connect a reservoir with the wrong colored ink to a respective printhead. This may occur, for example, when the operator is in a rush to complete a high volume operation. Or perhaps, the operator might think that a container holds a dark colored ink when it actually holds a light colored ink. Thus, in a subsequent printing operation, the controller or CPU may not know that a particular printhead is depositing a wrong colored ink on the substrate. Moreover, the problem may not be noticed and resolved until one or more images are generated. Since these images are generated with one or more incorrect colors, they are typically discarded, which increases the cost of the printing operation.
Other factors which may impact the cost of operating the printer include the use of ink that has exceeded its expiration date. Typically, the operator does not know how old the ink being used is. Generally, the operator keeps a log of when a particular ink container has been placed in the printer. Not infrequently, the operator may not refer to the log, and out of date ink may end up being used to the detriment of the printed image.